The present invention relates to apparatus and methods for converting tow into sliver and particularly relates to apparatus and methods for converting continuous filament tow into staple fibers having substantially uniform orientation relative to one another and drafted to form a substantially homogeneous sliver.
Continuous filament tow has been converted previously into staple sliver by an apparatus known in the textile trade as the Pacific Converter. Such process is described and illustrated in U.S. Pat. No. 2,438,469, granted Mar. 23, 1948. However, stock processed through that machine was of poor quality and required multiple process steps to render it suitable for use in apparel fabrics, e.g., worsted fabrics.
Subsequently, another converter was developed and placed into use on a production basis and which converter constituted a substantial improvement over the Pacific Converter. This improved apparatus is described and illustrated in U.S. Pat. No. 3,522,634, granted Aug. 4, 1970, of common assignee herewith. While the production speed of that improved apparatus is substantial, it too has certain drawbacks. For example, for apparel fabrications, a substantial majority of the tows processed by the apparatus according to that patent still require recombing after blending with other fiber types. Additionally, while the machine operates at substantial speed, the productivity of the machine is not great. That is, the machine delivers lightweight sliver, on the order of 200 grains per yard. The speed of the apparatus cannot be increased because it employs a gill head having faller bars which constitute a limitation on the maximum speed attainable during the combing operation. Another principal drawback of that apparatus, which has been recognized for years, is that the mechanical gill heads and apron drafting used in that machine are very expensive and are very high-maintenance items. The high frequency of the required maintenance substantially increases the downtime of the machine, and, when coupled with the actual cost of repairs, provides for avery expensive machine operation. Also, these prior machines are undesirably sensitive to tow finish, denier, temperature and humidity.
It will also be appreciated that in any tow to staple converter, it is important to maintain the fibers parallel to one another in the drafting zone. It will also be appreciated that the cutter and anvil of these prior converters essentially apply great pressure to the tows passing through the nip to weaken the individual fibers. In such prior machines discussed above-where two or more tows are passed through the cutters, control of the tow stock through the cutter and anvil is to a large extent lost. That is, because of the combined thickness of the tows, the individual fibers are cut to a greater or lesser extent depending upon their position in the tow relative to the cutter and anvil. The uniformity of these points of weakness thus varied across the tow. Also, certain of the tow fibers would be cut entirely through, whereas others would be cut partially through and then to a greater or lesser extent according to their location in the combined tows. No uniformity of cutting action exists across the tows. As a result, certain of the fibers which were through-cut by the cutters would turn or curl sideways as they left the cutter and upon entry into the drafting zone, resulting in a high probability of defects in the sliver. That is, portions of the stock would separate between the cutter and faller bars and the pull of the input rolls to the faller bar head would separate the fibers prematurely, causing them to enter the faller bars sideways. All of this was caused by the non-uniform cutting action between the cutter and anvil.
The present invention constitutes an improvement in both apparatus and methods for converting tow to sliver, and affords substantial advantages in higher production capability, a higher quality product than capable with the prior apparatus and methods, and an apparatus which is mechanically simple, efficient, easier to repair at less cost, and which requires only minimum downtime for repairs. Particularly, in the apparatus and process of the present invention, one or more tows are provided for passage through individual cutters. Each cutter includes an anvil roll and a cutter roll provided with one or more helical lands such that, when the tow web passes between the rolls, diagonally parallel cuts substantially through the continuous filament are provided. The cut tow webs from the cutters are then superposed over one another. The diagonal cuts preferably lie in opposite directions such that, upon superposition of the webs, the diagonal cuts, in plan, extend in opposite diagonal directions. The unique cutter system fractures the tow into cut lengths but does' not completely sever the low fibers. This enables the cut tow fibers to be pulled forward across the collector pan into the drafting zone without separating.
The superposed tow webs then pass over a collector pan having a convex upper surface and lateral margins which extend inwardly toward one another below the upper surface. When the tow passes over the collector pan, its lateral margins or selvages turn or fold under to follow the contour of the collector pan. This locates such tow margins in registration with and below the main body of the tow upon exiting the collector pan.
The cut tow then passes through a first pair of draft rolls flanked on upstream and downstream sides by a pair of smooth, vertically extending, rolls which decrease the lateral extent of the tow. The tow then passes through a pair of pin rolls where the staple fiber is debonded and combed. The tow then passes through sets of drafting rolls and through a condensor to gather and reduce the sliver cross-section for exit through the final drafting rolls. The sliver, which is now made up of staple lengths oriented due to the various drafting stages, is fed into a crimper for compacting so that it may be run at high speeds and is then disposed in coiled form in a sliver can by a coiler.
It will be appreciated that, in the overall general arrangement of the present invention as previously described, there are various features and advantages of the present invention in comparison with the converter system, as set forth in U.S. Pat. No. 3,522,634 including higher productivity. For example, while the prior production version of the converter disclosed in U.S. Pat. No. 3,522,634 delivered four tow webs simultaneously at about 14.5 feet per minute, for a total of 5,608 grains per yard, it delivered only 200 grains per yard of sliver at 175 yards per minute, providing a draft of 22. The present invention, however, may provide tow at 102 feet per minute input from each of two tow cartons, with 2,804 grains per yard delivered, providing a 600 grain per yard sliver at 170 yards per minute, with a draft of 8.3. Thus, the total weight delivery of the sliver in accordance with the present invention is desirably much higher than previously obtained with the apparatus of U.S. Pat. No. 3,522,634. That higher output delivery is also obtained with relative mechanical simplicity and ease of repair. It also provides a better quality product. For example, each tow is cut at a single cutter in the present invention (in contrast to providing two or more tows through a single cutter). This improves productivity by reducing the required cutter pressure and hence increases the life of the cutter, as well as reduces the number of undesirable neps, pinpoints and short and long fibers.
Additionally, the construction of the present apparatus enables attachment of a blending device, for example, to blend wool with the polyester tow being cut and processed as described above. Such device may be located, for example, just beyond the pin rolls and before the following draft rolls. Thus, wool can be fed behind and into the draft rolls following the pin rolls on top of the cut staple fibers, making a sandwich of polyester and wool. As the combined wool and polyester sheets are drafted, they become a semi-intimate blend passing through the various draft rolls into a coiler at the desired delivery weight.
Apart from an overall improved apparatus, several individual features of the apparatus afford various advantages in construction, operation and result. For example, when tow is cut by cutter rolls, the leading edge of the cut tow tends to separate and fold backwards. This is a particular problem along the outer lateral margins or selvages of the cut tow, where the fiber ends may extend sideways or curl such that, when the fibers are presented for drafting, defects, e.g., fiber clusters, neps and pinpoints, readily occur. That is, the defects are usually due to the tow pulling apart prematurely before drafting such that the fibers are not straight for drafting. Rather, the fiber ends may be turned sideways.
The unique construction of the collector pan tends to minimize or eliminate the tendency of the leading edge and lateral margins of the cut tow to curl or lay back sideways. More particularly, the collector pan is in the form of an upwardly curved convex surface having lateral margins which are folded or turned inwardly below the convex curved surface. As the superposed cut tow ends emerge from the cutters for presentation to the drafting section, the tow slides across the top convex surface of the collector pan. Due to the shape of the pan, the margins of the sheet of cut fibers roll around the sides of the collector pan. Thus, the leading edges of the cut tow and the marginal portions of the web turn or fold about the lateral margins of the pan to a location below the main portion of the pan. The margins or selvage portions of the superposed tow ends thus lie in registration with the main body of the tow as the tow exits the collector pan.
It will also be appreciated, upon comparing the present invention with the converter illustrated in prior U.S. Pat. No. 3,522,634, that the present invention eliminates the previously utilized gill head in its entirety. Consequently, the mechanical problems associated with the use of a gill head, such as high repair costs and high maintenance components are eliminated. Importantly, the limitation on gill head speed is similarly eliminated in favor of the pin rolls of the present invention which are capable of higher operational speeds. The pin rollers, of course, comb and debond the cut fibers. In accordance with the present invention each pin roller comprises a plurality of discs mounted on a shaft and spaced one from the other in an axial direction. The pins of the opposed rolls lie in meshing engagement with one another while the axial spacing of the pins permits ample space between the pins to receive and comb the cut fibers. It is important in the present invention that the pins have a leading edge which is inclined back from the direction of rotation of the rollers such that the pins pass into the stock on the front side of the point of the pin. That is, the leading edge of each pin first engages the stock, followed by the tip of the pin. Otherwise, entry of the pin tip into the stock before the body of the pin would cause defects such as neps and pinpoints in the sliver.
Another important advantage of the present invention, apart from high production and improved quality, is that little or no crimp is lost from the fiber during processing. This is believed to be a result of the low fiber stretch on the apparatus. Crimp retention during processing is particularly important in subsequent processing of fine deniers. Consequently, this crimp retention capacity improves the processability of the sliver as well as its processability through roving and spinning operations.
Another important advantage of the present invention resides in the employment of a single tow being presented to the cutter. This results in a uniform cutting action across the tow as the tow emerges from the cutter substantially maintaining the tow stock parallel as it enters the drafting zone. More particularly, the tow is pressed between the cutter and anvil and a substantially uniform cut is provided the fibers across the tow as it passes through the cutter. The fibers are not cut entirely through but form weakened zones by the action of the cutter and anvil which enable the fibers to be severed by the pulling action in the drafting zone rather than prematurely before the drafting zone. Consequently, the fibers are maintained parallel one to the other upon exiting the cutter and entering the drafting zone, i.e., the pin roller arrangement. Thus, the fibers are controlled effectively as they pass through the cutter such that the cutter effects a substantially uniform cut in all of the fibers. Relatively few of the fibers are cut thus through by the cutter, thereby substantially minimizing or eliminating a sideways orientation of the fibers or a curl which might cause defects in the sliver when such improperly oriented fibers pass through the drafting zone. In short, the present invention provides uniform cuts at longitudinally and transversely spaced positions along the tow, which cuts are characterized by an essentially weakened fiber portion, enabling separation of the fibers in the drafting zone, i.e., by the pin roller arrangement hereof, minimal or no separation of the fibers prior to entry into the drafting zone.
Therefore, in accordance with a preferred embodiment of the present invention, there is provided apparatus for converting tow to sliver, comprising means for feeding a web of tow from a supply through the converting apparatus, means for cutting the web into staple fibers of substantially uniform length, means for turning the cut staple fibers along at least one marginal portion of the cut tow web into registration with a main portion of the tow web inwardly of the marginal portion, and a drafting section for receiving the turned tow web for forming the sliver.
In a further preferred embodiment of the present invention, there is provided apparatus for converting tow to sliver, comprising means for feeding a web of tow from a supply through the converting apparatus, and means for cutting the web into staple fibers of substantially uniform length, together with a drafting section for drafting the cut staple fibers to form a sliver. The drafting section includes a pin roll and a pair of drafting rolls immediately following the pin roll in the downstream direction of movement of the tow web, together with means for rotating the pin roll and the draft rolls. The pin roll has a plurality of projections extending therefrom, the projections being spaced circumferentially one from the other about the pin roll and spaced axially one from the other therealong. Each projection has a tip and leading and trailing edges extending therealong toward the tip, and each leading edge extends in a direction to engage the tow web first along the leading edge followed by engagement of the tip with the tow web as the pin roll is rotated and the projections engage the web.
In a still further preferred embodiment of the present invention, there is provided a method of processing tow to sliver in a converter, comprising feeding a web of tow from a supply through the converter, cutting the web into staple fibers of substantially uniform length, turning the cut staple fibers along at least one marginal portion of the cut tow web into registration with a main portion of the tow web inwardly of said marginal portion and passing the turned tow web through a drafting section to form the sliver.
In a still further preferred embodiment of the present invention, there is provided a method for processing tow to sliver in a converter, comprising feeding a web of tow from a supply through the converter, cutting the web into staple fibers of substantially uniform length and drafting the cut staple fibers to form a sliver including, in the drafting section, providing a pin roll and a pair of drafting rolls following the pin roll in the downstream direction of movement of the tow web, rotating the pin roll and the draft rolls at a peripheral speed greater than the linear speed of the cut tow web passing through the drafting section, forming a plurality of projections on the pin roll spaced circumferentially one from the other thereabout and extending axially therealong including forming on each projection a tip and leading and trailing edges extending therealong toward the tip, and engaging the web first along the leading edge followed by the tip as the pin roll is rotated and the projections engage the web.
In a still further preferred embodiment of the present invention, there is provided a method of cutting tow and presenting the cut tow to a drafting zone comprising the steps of passing tow having substantially parallel oriented tow fibers through the nip of a cutter and anvil and applying a substantially uniform pressure to the tow fibers as they pass through the nip to provide substantially uniform weakened zones in substantially each tow fiber at longitudinally spaced positions therealong and substantially without complete severing thereof whereby the cut, unsevered tow fibers are maintained connected and in parallel relation one to the other upon presentation to the drafting zone.
Accordingly, it is a primary object of the present invention to provide novel and improved apparatus and methods for converting continuous filament tow into staple fiber characterized by increased speed of operation, greater delivery weight of staple fiber, lower frequency of repair and maintenance, and a higher quality sliver with minimal defects in comparison with prior tow converters.
These and further objects and advantages of the present invention will become more apparent upon reference to the following specification, appended claims and drawings.